The present invention relates to a refrigerating machine oil composition for a refrigerating machine and an air-conditioner, a working medium for a refrigeration system of a refrigerant compressing type and a refrigerator and a compressor, and, more particularly, to a refrigerator, a room air-conditioner and a package air-conditioner.
The use of CFC12 (dichlorodifluoromethane) for a refrigerator or a car air-conditioner has been abolished completely according to the chlorofluorocarbon regulation. Further, the use of HCFC22 (monochlorodifluoro-methane), which is being used for an air-conditioner or the like at the present time, is also to be abolished completely from the viewpoint of environmental protection. An alternative refrigerant under consideration is an HfC (hydrofluorocarbon) group refrigerant having a boiling point temperature near those of CFC12 and HCFC22 or a mixed refrigerant obtained by mixing two or more kinds of the HFC group refrigerants.
A refrigerating machine oil is used in a compressor of a refrigerating machine or an air-conditioner, such as a refrigerator, a room air-conditioner, a package air-conditioner, a freezer or the like, to lubricate, seal and cool the moving parts. In recent years, refrigerating machine oil has come to be used under more severe conditions with increasing demand for energy-saving, reduced size, low noise and high efficiency operation of the compressor. Therefore, a refrigerating machine oil which has a good lubricity, and is particularly good in wear resistance, is required in order to maintain the reliability of the compressor. In regard to a refrigerating machine oil, a naphthene group mineral oil, a paraffin group mineral oil and alkylbenzene have been widely used, since they have a better miscibility with the CFC (chlorofluorocarbon) group and the HCFC (hydrochloroflouoro-carbon) group refrigerants and are low in cost. However, these refrigerating machine oils cannot be dissolved in the HFC group refrigerants proposed as an alternative refrigerant. Polyol-ester of an aliphatic group synthetic oil having a polar group in the molecule has been developed as a refrigerating machine oil which is miscible with the HFC group refrigerants, and is disclosed in Japanese Patent Application Laid-Open No. 62-13912, PCT National Patent Publication No. 3-505602 and Japanese Patent Application Laid-Open No. 4-183788.
Further, since a HFC group refrigerant does not contain chloride in the molecule, a lubrication effect produced by the refrigerant itself cannot be expected at all compared to the conventional refrigerants. Therefore, the refrigerating machine oil is required to have a better lubricity.
Various kinds of additives are used in common refrigerating machine oils, and a lubricity improving agent is one of them. For example, phosphor compounds of a tertiary phosphate group, such as triphenylphosphate, tricresylphosphate and the like, are known lubricity improving agents (SAKURAI, Toshio, Additives for Petroleum Products, Saiwai Shobou, May 15, 1973). In regard to lubricity improving agents for the refrigerating machine oils applicable to HFC group refrigerants, there are (1) secondary phosphites and acidic phosphates (Japanese Patent Application Laid-open No. 4-28792), (2) phosphate ester of polyoxyalkylenealkyl ether (Japanese Patent Application Laid-Open No. 62-79295), (3) secondary phosphites or amine salts of acidic phosphites (Japanese Patent Application Laid-Open No. 63-90597, Japanese Patent Application Laid Open No. 3-39400). (4) organic molybdenum compounds (Japanese Patent Application Laid-Open No. 5-39494) and so on. However, none of these additives exhibits sufficient effects with respect to wear resistance and reliability, particularly in comparison to polyole-ester. In addition to this, there is the disadvantage that the reliability of the compressor is decreased, since these additives are low in thermal stability and in miscibility with hydrofluorocarbon group refrigerants or refrigerating machine oils.
Of the compressors for refrigerators and air-conditioners, there are a displacement type compressor such as a scroll type, a reciprocal type, a screw type, and vane rotary type compressors, and a volume type compressor such as a turbo type compressor. Particularly, the scroll type compressor among these compressors requires a refrigerating machine oil having an excellent wear resistance because slide bearings are used under a severe friction condition.